Semiconductor memory device

ABSTRACT

A semiconductor memory device includes a memory cell array divided into a plurality of subarrays arranged in matrix form, the plurality of subarrays making up a plurality of subarray columns, an address pad column formed outside the memory cell array, the address pad column comprising a plurality of address pads that are arranged to be substantially parallel to the subarray columns, a data I/O pad column formed in a middle section of the memory cell array, the data I/O pad column comprising data I/O pads that are arranged to be substantially parallel to the subarray columns, an address input circuit arranged in the middle section of the memory cell array, and a pad input address line formed in a direction substantially perpendicular to the subarray columns on the memory cell array, the pad input address line directly connecting the address pad and the address input circuit.

BACKGROUND

1. Field of the Invention

The present invention relates to semiconductor memory devices, and morespecifically, to a layout technique of memory cells and peripheral I/Osin a semiconductor memory device.

2. Description of Related Art

Although memory cells have been reduced in size in accordance withminiaturization of processes in semiconductor manufacturing, reductionin size of pads for packaging or the like is not sufficient. Further,increase in the number of pads has been significant in accordance withthe increase of the number of product functions, and it is desired tomount as many pads as possible without increasing the size of the chip.

FIG. 4 shows a pattern layout of a semiconductor memory chip assembledin a flip chip package disclosed in Japanese Patent No. 3990125 (Yabe etal.) (patent document 1). In this memory chip, a memory cell array isdivided into a plurality of subarrays arranged in matrix form. In thisexample, the memory cell array is divided into subarrays SA1,1 toSA16,16 of a matrix with 16 rows and 16 columns. Thus, the p-th subarraycolumn (p is an integer smaller than 17) includes sixteen subarraysSAp,1 to SAp,16.

A first peripheral circuit area 11 is formed in a middle section of asubarray matrix, which extends in the column direction, and a secondperipheral circuit area 12 is formed in a middle section of the subarraymatrix, which extends in the row direction. The first peripheral circuitarea 11 supplies a subarray control signal to each of sixteen subarraysSAp,1 to SAp,16 included in the p-th subarray column.

In this example, the first peripheral circuit area 11 is interposedbetween the eighth and ninth rows of the subarray matrix and includessense amplifiers. The second peripheral circuit area 12 is interposedbetween the eighth and ninth columns of the subarray matrix and includesmain row decoders. External connection pads are arranged in a middlesection of the subarray matrix, which extends in the column direction.In this example, a first pad area 21 is formed between the fourth andfifth rows of the subarray matrix and a second pad area 22 is formedbetween the twelfth and thirteenth rows thereof.

Paying attention to the first subarray column as a representativeexample, the first peripheral circuit area 11 supplies subarray controlsignals from control signal drivers DRV1 to DRV16 to sixteen subarraysSA1,1 to SA1,16 via subarray control signal lines S1,1 to 51,16,respectively.

Subarray control signal lines S1,1 to S1,4 extend to their respectivesubarrays (SA1,1 to SA1,4), which are located away from the firstperipheral circuit area 11, from the first periphery circuit area 11through the first pad area 21. Subarray control signal lines S1,13 toS1,16 extend to their respective subarrays (SA1,13 to SA1,16), which arelocated away from the first peripheral circuit area 11, from the firstperiphery circuit area 11 through the second pad area 22.

FIG. 5 is an enlarged view showing an example of the pattern layout in aneighborhood of the first pad area 21 shown in FIG. 4. For the sake ofsimplification of layout design, a plurality of subarray control signallines Sp,1 to Sp,16 are arranged on the p-th subarray column at the samepitches as those of the subarray columns and thus designedhierarchically.

The first pad area 21 includes a plurality of pads Pd and these pads arearranged in the row direction at the same pitches as those of thesubarray columns. In the first embodiment, the pads Pd are located ontheir respective boundaries of the subarray columns, as indicated by thedotted lines in FIG. 4. The second pad area 22 includes a plurality ofpads Pd and these pads Pd are arranged in the row direction at the samepitches as those of the subarray columns and located on their respectiveboundaries of the subarray columns, as indicated by the dotted lines inFIG. 4.

At least some (Sp,1 to Sp,4 and Sp,13 to Sp,16) of the subarray controlsignal lines Sp,1 to Sp,16, which are connected between the firstperipheral circuit area 11 and the subarrays of the subarray columns,are formed linearly such that they can pass between the pads Pd of thefirst pad area 21 and between the pads Pd of the second pad area 22.

In this example, all the subarray control signal lines Sp,1 to Sp,16 areformed to have the same length as that of a signal line connecting thesubarrays SAp,1 and SAp,16 that are farthest from the first peripheralcircuit area 11. Furthermore, all the subarray control signal lines Sp,1to Sp,16 are formed linearly such that they can pass between the padsPd. The memory chip disclosed in Yabe et al. can be summarized asfollows. The memory cell array is divided into subarrays SA1,1 toSA16,16 arranged in matrix form. The peripheral circuit areas 11 and 12and pad areas 21 and 22 are formed in the middle sections of thesubarray matrix. In the pad areas 21 and 22, the plurality of pads Pdare arranged at the same pitches as those of the subarrays, and thesubarray control signal lines Sp,1 to Sp,16, which connect theperipheral circuit area 11 and each of the subarrays, are linearlyformed such that they can pass between the pads Pd.

The same pattern can thus be designed for each subarray column in layingout the subarray control signal lines Sp,1 to Sp,16. As such, thesubarray control signal lines Sp,1 to Sp,16 are not turned so as todetour around the pads of the pad areas 21 and 22 formed halfway throughthe subarray columns, they can be prevented from increasing in parasiticcapacitance and parasitic resistance of the signal lines. Thus, thevariations of delay time of subarray control signals supplied to thesubarrays can be suppressed, with the result that a high-speed memorychip can be designed.

In order to achieve a high-speed memory such as an SRAM, an SRAM chipcapable of a high-speed operation as this example is formed. Then, theSRAM chip is bonded to a chip assembly substrate (not shown) by flipchip bonding and assembled in a package (usually resin-molded). Thesubarray control signal lines Sp,1 to Sp,16 are formed to have the samelength as that of a signal line connecting the subarrays that arefarthest from the first peripheral circuit area 11, thereby keeping theparasitic capacitances and parasitic resistances of the respectivesignal lines constant. Meanwhile, Japanese Unexamined Patent ApplicationPublication No. 8-116036 (patent document 2) discloses a technique ofarranging pads on both sides of a memory array.

SUMMARY

In the above-described semiconductor memory chip, a plurality of padsare arranged at pitches corresponding to those of the plurality ofsubarray columns in the pad area, and the signal lines are each formedlinearly such that they can pass between the pads in the pad area.Accordingly, when the number of pads increases with respect to thememory cell area, the area where the signal lines that pass between thepads is formed cannot be secured unless the chip size is increased.

A semiconductor memory device according to a first aspect of anembodiment of the present invention is a semiconductor memory deviceincluding a memory cell array that is divided into a plurality ofsubarrays arranged in matrix form, the plurality of subarrays making upa plurality of subarray columns, a first pad column that is formedoutside the memory cell array, the first pad column including aplurality of first pads that are arranged to be substantially parallelto the subarray columns, a second pad column that is formed in a middlesection of the memory cell array, the second pad column including secondpads that are arranged to be substantially parallel to the subarraycolumns, a circuit that is arranged in the middle section or at theoutside of the memory cell array, and a line that is formed in adirection substantially perpendicular to the subarray columns on thememory cell array, the line being directly connected to the circuit.

Accordingly, it is possible to minimize the increase of the chip sizeeven with the increased number of pads, and to maintain the area wherethe signal line is formed. Furthermore, as the line is directlyconnected to the circuit, the signal delay can be reduced.

A semiconductor memory device according to a second aspect of anembodiment of the present invention is a semiconductor memory deviceincluding a memory cell array that is divided into a plurality ofsubarrays arranged in matrix form, the plurality of subarrays making upa plurality of subarray columns, an address pad column that is formedoutside the memory cell array, the address pad column including aplurality of address pads that are arranged to be substantially parallelto the subarray columns, a data I/O pad column that is formed in amiddle section of the memory cell array, the data I/O pad columnincluding data I/O pads that are arranged to be substantially parallelto the subarray columns, an address input circuit that is arranged inthe middle section of the memory cell array, and a pad input addressline that is formed in a direction substantially perpendicular to thesubarray columns on the memory cell array, the pad input address linedirectly connecting the address pad and the address input circuit.

Accordingly, it is possible to minimize the increase of the chip sizeeven with the increased number of pads, and to secure the area where thesignal line is formed. Further, as the pad input address line directlyconnects the address input circuit and the address pad, the signal delaycan be reduced.

According to the present invention, it is possible to maintain the areawhere the signal line is formed without increasing the chip size.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other exemplary aspects, advantages and features will bemore apparent from the following description of certain exemplaryembodiments taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 shows a layout of a semiconductor memory device according to afirst exemplary embodiment;

FIG. 2 shows a layout of a semiconductor memory device according to asecond exemplary embodiment;

FIG. 3 shows a layout of a semiconductor memory device according to athird exemplary embodiment;

FIG. 4 shows a layout of a semiconductor memory device according to apatent document 1; and

FIG. 5 shows a layout of a pad area in FIG. 4.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Hereinafter, a semiconductor memory device according to the exemplaryembodiments of the present invention will be described with reference tothe drawings. The same components throughout the drawings are denoted bythe same reference symbols, and the description thereof will be omittedas appropriate. In the drawings, some of the elements of thesemiconductor memory device according to the exemplary embodiments areenlarged as appropriate for the purpose of description.

First Exemplary Embodiment

A semiconductor memory device according to the first exemplaryembodiment of the present invention will be described with reference toFIG. 1. FIG. 1 is a diagram showing an example of a layout of asemiconductor memory device 1 according to the first exemplaryembodiment. The semiconductor memory device 1 according to the firstexemplary embodiment shown in FIG. 1 includes a logic circuit and anaddress register circuit A7, an address input circuit A8, an I/O circuitA9, a data I/O pad column A10, an address pad column A11, and a memorycell array A13.

The memory cell array A13 includes an address decoder circuit A3 and acell data reading sense amplifier circuit A6. The memory cell array A13further includes subarrays formed of a plurality of memory cells thatare not shown. The plurality of subarrays are arranged in matrix. InFIG. 1, a plurality of subarrays that are arranged in vertical direction(column direction) is called subarray column, and a plurality ofsubarrays that are arranged in lateral direction (row direction) iscalled subarray row. In summary, the memory cell array A13 includes aplurality of subarray columns A12.

In the example shown in FIG. 1, the memory cell array A13 is dividedinto two parts by the data I/O pad column A10. One memory cell array A13is formed by subarrays of 1 row×4 columns. Further, this memory cellarray A13 is arranged in 1 row×2 columns. In other words, the memorycell array A13 is arranged in each of the right side and the left sideof the data I/O pad column A10. Further, the four subarray columns A12are arranged in each of the memory cell arrays A13.

In each of the subarray columns A12, the address decoder circuit A3 andthe cell data reading sense amplifier circuit A6 are arranged. In thefirst exemplary embodiment, the address decoder circuit A3 is arrangedin the middle section of each subarray column A12. Further, the celldata reading sense amplifier circuit A6 is formed along with the samedirection in which each of the subarray columns A12 is formed.

In the area between two memory cell arrays A13, the data I/O pad columnA10 is arranged. In summary, the data I/O pad column A10 is arranged inthe middle section of the memory cell arrays A13. The data I/O padcolumn A10 includes a plurality of I/O pads A16 that are arranged in thesame direction in which the subarray column A12 is arranged. In thisexample, 20 I/O pads A16 are arranged in two lines, each line including10 pads, in the same direction in which the subarray column A12 isarranged.

The address pad columns A11 are arranged outside the memory cell arraysA13. More specifically, the address pad column A11 is arranged in eachof the right area of the right memory cell array A13 and the left areaof the left memory cell array A13. In summary, the data I/O pad columnA10 and each of the address pad columns A11 are arranged to be opposedwith each other with the memory cell arrays A13 interposed therebetween.

The address pad column A11 includes a plurality of address pads A14 thatare arranged in the same direction in which the subarray column A12 isarranged. In this example, 20 address pads A14 are arranged in twolines, each line including 10 pads, outside the left and right memorycell arrays A13 in the same direction in which the subarray column A12is arranged. The address pads A14 are formed in chip ends.

In the middle section in the column direction of the area where the dataI/O pad column A10 is arranged, the logic circuit and the addressregister circuit A7 is arranged. Further, the I/O circuits A9 arearranged to be adjacent to the column direction of each I/O pad A16. InFIG. 1, the I/O circuits A9 are arranged in the upper side of the I/Opads 16 in the column direction in the upper side of the logic circuitand the address register circuit A7. Further, the I/O circuits A9 arearranged in the lower side of the I/O pads A16 in the column directionin the lower side of the logic circuit and the address register circuitA7.

Between the data I/O pad column A10 and each of the memory cell arraysA13, a plurality of address input circuits A8 are provided. In summary,the address input circuits A8 are arranged in the middle section of thememory cell arrays A13. In this example, 10 address input circuits A8are arranged in each of an area between the data I/O pad column A10 andthe right memory cell array A13 and an area between the data I/O padcolumn A10 and the left memory cell array A13. These address inputcircuits A8 are arranged in the same direction in which the subarraycolumn A12 is arranged.

The address pad A14 and the address input circuit A8 are connected by apad input address line A4. The pad input address line A4 is formed in adirection that is perpendicular to the data I/O pad column A10, theaddress pad column A11, and the subarray column A12 on the memory cellarray A13. The pad input address line A4 connects the address pad A14and the address input circuit A8 without passing through the circuitelement.

The address input circuit A8 is connected to the logic circuit and theaddress register circuit A7 through an address line A15. The logiccircuit and the address register circuit A7 and the address decodercircuit A3 that is in the subarray column A12 are connected by a cellselection address line A2. The cell selection address line A2 is formedin a direction that is perpendicular to the subarray column A12.

Each cell data reading sense amplifier circuit A6 that is in eachsubarray column A12 and the I/O circuit A9 are connected by a data busline A5. The data bus line A5 is formed in a direction that isperpendicular to the subarray column A12. Although not shown in FIG. 1,a signal line (word line) to read out information from each memory cellis arranged in the vertical direction (column direction) of FIG. 1 fromeach memory cell, and a bit line is arranged in the lateral direction(row direction).

In the above-discussed layout, the memory cell arrays A13 are arrangedin matrix form, and the data I/O pad column A10 is formed in the middlesection of the memory cell arrays A13 and the address pad columns A11are formed in the both ends of the memory cell arrays A13. Each of thedata I/O pad column A10 and the address pad column A11 is arranged inparallel with the subarray column A12.

Further, the pad input address line A4 is formed in a direction that isperpendicular to the subarray column A12 on the memory cell array A13.The pad input address line A4 directly connects the address pad A14 inthe chip end and the address input circuit A8 that is arranged in themiddle section of the memory cell arrays A13 which are divided withoutpassing through the circuit element.

As stated above, the pad line is divided into the data I/O pad columnA10 and the address pad column A11, which are arranged separately in themiddle section and outside of the memory cell arrays, respectively.Thus, there are memory cell arrays A13 between the data I/O pad columnA10 and the address pad columns A11, which prevents the pad lines frombeing concentrated with each other. Accordingly, the area where thesignal line is formed may be maintained.

In the related art, the pads and the input circuit are arranged in thesame area, and the signal is drawn from the input circuit by performingbuffering. However, according to the first exemplary embodiment, theaddress pads A14 which are the signal pads are arranged outside thememory cell arrays A13. Further, the line is connected to the inputcircuit by passing on the memory cell array A13 from the address padA14. Accordingly, the delay can be reduced.

Second Exemplary Embodiment

A semiconductor memory device according to the second exemplaryembodiment of the present invention will be described with reference toFIG. 2. FIG. 2 is a diagram showing the configuration of a semiconductormemory device 1′ according to the second exemplary embodiment. In FIG.2, the same components as those of FIG. 1 are denoted by the samereference symbols, and the description thereof is omitted.

In developing a product to change the memory capacitance, it may berequired to increase or decrease the number of columns of the subarraycolumn A12 and to move the address pads A14. In the second exemplaryembodiment, the memory cell array A13 which is formed by the subarraycolumns A12 of 1 row×4 columns in the first exemplary embodiment ischanged to the subarray columns A12 of 1 row×2 columns. In short, thearea of the memory cell array A13 is reduced to decrease the chip size.

As shown in FIG. 2, the memory cell array A13 is divided into two partsby the data I/O pad column A10. One memory cell array A13 is formed bysubarrays of 1 row×2 columns. Further, this memory cell array A13 isarranged in 1 row×2 columns. More specifically, the memory cell arrayA13 is arranged in each of the right side and the left side of the dataI/O pad column A10. Further, two subarray columns A12 are arranged ineach of the memory cell arrays A13.

Further, the address pad columns A11 are moved to the middle section ofthe memory cell arrays A13 where the data I/O pad column A10 is formedin accordance with the reduced amount of the memory cell arrays A13 inthe area outside the memory cell arrays A13.

The pad input address line A4 and the data bus line A5 that are formedin the direction that is perpendicular to the subarray column A12 aremade shorter in accordance with the reduced number of columns of thesubarray columns A12. According to such a configuration, even when thememory cell capacity is changed, the chip may be formed by just changingthe number of columns of the subarray column A12. Further, even when thememory cell capacity is reduced and the number of pads is not changed,the area where the signal line is formed can be maintained withoutincreasing the chip size.

In such a case that the product is developed by increasing or decreasingthe memory cell capacity, there is no pad column and peripheral circuitin a side where the chip size is reduced. Accordingly, the area wherethe signal line is formed may be secured without giving an influence onthe peripheral circuit area. Further, it is possible to form the chip ina simple manner by just reducing the memory cell array area.

Third Exemplary Embodiment

A semiconductor memory device according to the third exemplaryembodiment of the present invention will be described with reference toFIG. 3. FIG. 3 is a diagram showing the configuration of a semiconductormemory device 10 according to the third exemplary embodiment. In FIG. 3,the same components as those of FIG. 1 are denoted by the same referencesymbols, and the description thereof will be omitted.

According to the product specification or the memory cell configuration,the address pad column A11 in which the plurality of address pads A14are arranged may be arranged in the area of the middle section of thememory cell arrays A13 that are divided into two lines in the firstexemplary embodiment. As shown in FIG. 3, the address pads A14 arearranged in the area between the memory cell arrays A13 that are dividedin two lines. In summary, the address pads A14 are arranged in themiddle section of the memory cell arrays S13. The address pad column A11includes a plurality of address pads A14 that are arranged in the samedirection in which the subarray column A12 is arranged. In the thirdexemplary embodiment, 20 address pads A14 are arranged in two lines,each line including 10 pads, in the same direction in which the subarraycolumn A12 is arranged.

On the other hand, the data I/O pad columns A10 are arranged in bothoutside parts of the memory cell arrays A13. More specifically, the dataI/O pad column A10 is arranged in each of the right area of the rightmemory cell array A13 and the left area of the left memory cell arrayA13. The data I/O pad column A10 includes a plurality of I/O pads A16that are arranged in the same direction in which the subarray column A12is arranged. In the third exemplary embodiment, 20 I/O pads A16 arearranged in two line, each line including 10 pads, in a way they arearranged outside the left and right memory cell arrays A13 in the samedirection in which the subarray column A12 is arranged. The I/O pads A16are formed in the chip ends.

Further, in the middle section in the column direction of the area wherethe address pads A14 are arranged, the logic circuit and the addressregister circuit A7 is arranged. Further, the I/O circuits A9 arearranged to be adjacent to the column direction of the I/O pads A16. InFIG. 3, the I/O circuits A9 are arranged in the upper side in the columndirection with respect to the address pads A14 in the upper side of thelogic circuit and the address register circuit A7. Further, the I/Ocircuits A9 are arranged in the lower side in the column direction withrespect to the I/O pads A16 in the lower side of the logic circuit andthe address register circuit A7. In short, the I/O pads A16 and the I/Ocircuits A9 are alternately arranged.

A plurality of address input circuits A8 are arranged between the twolines of the address pads A14. In accordance with the address pads A14,20 address input circuits A8 are arranged in two lines. Although notshown in FIG. 3, the address pad A14 and the address input circuit A8are directly connected by the pad input address line. Accordingly, thesimilar effect as that of the first and second exemplary embodiments maybe obtained.

As discussed above, according to the present invention, each pad columncan be arranged separately in the middle section and the outside of thememory cell array, whereby it is possible to secure the signal line areawithout affecting the chip size even with the increased number of padswith respect to the area of the memory cell array. Furthermore, the padsand the input circuits can be directly connected by the lines passing onthe memory cell without passing through the circuit element, whereby thesignal delay can be reduced. Further, probe cards may be manufactured inan easy way as the pad column arranged in the middle section of thememory cell arrays is apart from the pad columns arranged in the chipends.

Further, as there is no pad column and peripheral circuit in a sidewhere the chip size is reduced, the area of the peripheral circuit isnot changed. Accordingly, when another chip is made by increasing ordecreasing the memory cell capacity, the chip can be formed in a simpleway by just reducing the memory cell array area. As each pad is arrangedseparately in the middle section and the chip ends of the memory cellarrays, it is possible to prevent the package substrate line from beingconcentrated around pads. Accordingly, the package substrate pattern canbe designed in a simple way.

The first, second and third exemplary embodiments can be combined asdesirable by one of ordinary skill in the art.

While the invention has been described in terms of several exemplaryembodiments, those skilled in the art will recognize that the inventioncan be practiced with various modifications within the spirit and scopeof the appended claims and the invention is not limited to the examplesdescribed above.

Further, the scope of the claims is not limited by the exemplaryembodiments described above.

Furthermore, it is noted that, Applicant's intent is to encompassequivalents of all claim elements, even if amended later duringprosecution.

1. A semiconductor memory device comprising: a memory cell array that is divided into a plurality of subarrays arranged in matrix form, the plurality of subarrays making up a plurality of subarray columns; a first pad column that is formed outside the memory cell array, the first pad column comprising a plurality of first pads that are arranged to be substantially parallel to the subarray columns; a second pad column that is formed in a middle section of the memory cell array, the second pad column comprising second pads that are arranged to be substantially parallel to the subarray columns; a circuit that is arranged in the middle section or at the outside of the memory cell array; and a line that is formed in a direction substantially perpendicular to the subarray columns on the memory cell array, the line being directly connected to the circuit.
 2. The semiconductor memory device according to claim 1, wherein the first pads are address pads, the second pads are I/O pads, the circuit comprises an address input circuit arranged in the middle section, and the line directly connects the address pad and the address input circuit.
 3. The semiconductor memory device according to claim 1, further comprising a memory cell data reading sense amplifier circuit that is arranged in the memory cell array, wherein the circuit comprises an I/O circuit arranged in the middle section, and the line directly connects the data reading sense amplifier circuit and the I/O circuit.
 4. The semiconductor memory device according to claim 2, further comprising a memory cell data reading sense amplifier circuit that is arranged in the memory cell array, wherein the circuit comprises an I/O circuit arranged in the middle section, and the line directly connects the data reading sense amplifier circuit and the I/O circuit.
 5. The semiconductor memory device according to claim 1, wherein the first pads are I/O pads, and the second pads are address pads.
 6. The semiconductor memory device according to claim 1, further comprising a memory cell data reading sense amplifier that is arranged in the memory cell array, wherein the circuit comprises an I/O circuit arranged in the outside, and the line directly connects the data reading sense amplifier circuit and the I/O circuit.
 7. The semiconductor memory device according to claim 5, further comprising a memory cell data reading sense amplifier that is arranged in the memory cell array, wherein the circuit comprises an I/O circuit arranged in the outside, and the line directly connects the data reading sense amplifier circuit and the I/O circuit.
 8. The semiconductor memory device according to claim 1, further comprising an address register and a control logic circuit arranged in the middle section of the memory cell array and connected to the address input circuit.
 9. A semiconductor memory device comprising: a memory cell array that is divided into a plurality of subarrays arranged in matrix form, the plurality of subarrays making up a plurality of subarray columns; an address pad column that is formed outside the memory cell array, the address pad column comprising a plurality of address pads that are arranged to be substantially parallel to the subarray columns; a data I/O pad column that is formed in a middle section of the memory cell array, the data I/O pad column comprising data I/O pads that are arranged to be substantially parallel to the subarray columns; an address input circuit that is arranged in the middle section of the memory cell array; and a pad input address line that is formed in a direction substantially perpendicular to the subarray columns on the memory cell array, the pad input address line directly connecting the address pad and the address input circuit. 